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    SubjectRe: [PATCH] Use NULL instead of integer 0 in security/selinux/
    On Thu, 8 Jul 2004, P. Benie wrote:

    > On Thu, 8 Jul 2004, Richard B. Johnson wrote:
    > > On Thu, 8 Jul 2004, Herbert Xu wrote:
    > > > What's wrong with using 0 as the NULL pointer?
    > >
    > > Because NULL is a valid pointer value. 0 is not. If you were
    > > to make 0 valid, you would use "(void *)0", which is what
    > > NULL just happens to be in all known architectures so far,
    > > although that could change in an alternate universe.
    >
    > False. "An integer constant expressions with the value 0, or such an
    > expression cast to type void *, is called a null pointer constant. If a
    > null pointer constant is assigned to or compared for equality with a
    > pointer, the constant is converted to a pointer of that type", and "Any
    > two null pointers shall compare equal."
    >
    > In other words, when you use 0 as a null pointer, you really do get a null
    > pointer. If you are working on an architecture where the bit pattern of
    > the integer 0 and null pointers are not the same, the compiler will
    > perform the appropriate conversion for you, so it is always correct to
    > define NULL as (void *)0.

    That's NOT what is says. It states that a NULL pointer is converted to
    the appropriate type before any comparison is made. It does NOT say
    that 0 is a valid null-pointer.

    >
    > Personally, I always use 0 and NULL for integers and null pointers
    > respectively, but that's because of long estalished conventions that make
    > the code readabile, rather than anything to do with validity of the code.
    >
    > Peter
    > -
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    >

    Cheers,
    Dick Johnson
    Penguin : Linux version 2.4.26 on an i686 machine (5570.56 BogoMips).
    Note 96.31% of all statistics are fiction.


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